1. Field of the Invention
The present invention relates generally to the field of cycling footwear, and more particularly to a cycling shoe that is configured to improve a cyclist""s leg posture when pedaling.
2. Description of the Related Art
FIG. 1 is a schematic partial front view of a typical human foot 100 having a hindfoot bone structure 102 and a forefoot structure consisting of a number of metatarsal bones 104. The alignment of the foot 100 is depicted while in a neutral (i.e., natural or resting) posture relative to a horizontal axis 106 and a vertical axis 108. The metatarsal bones 104 of the forefoot are shown tilted at an angle a with respect to the horizontal 106 while the hindfoot 102 is generally aligned along the vertical axis 108. This illustrates the natural xe2x80x9cvarusxe2x80x9d tilt of the forefoot that is observed in 80%-90% of human feet while in the neutral posture. In other words, most of the human population has a slight natural tilt of the forefoot while the foot is at rest, as shown in FIG. 1. The varus tilt is typified by an elevated medial portion or instep of the foot, and a lowered lateral foot portion. In most persons, the natural varus angle is about 1.5xc2x0-5xc2x0.
FIG. 2 illustrates the effect of a varus forefoot on the motion and geometry of a bicycle rider""s leg while pedaling a bicycle. A right leg 200 is shown with the foot 100 positioned on a pedal 202 that is situated horizontally, i.e. parallel to a flat ground surface. The right leg 200 also consists of an ankle joint system 204, a tibia 206, a fibula 208, a knee joint 210, a femur 212, a hip joint 214, and a pelvic bone 216. When the rider presses down on the pedal 202, the forefoot 104 is made to lay flat across the horizontal pedal 202, and the ankle joint system 204 responds by rotating the lower leg (tibia 206 and fibula 208) and tilting it in the medial direction. The femur 212 likewise tilts medially to follow the lower leg, and the rider assumes the xe2x80x9cknock-kneedxe2x80x9d posture shown in FIG. 2, during the downstroke portion of a pedaling motion. Although the varus tilt of the forefoot is typically at a very small angle (1xc2x0-2xc2x0 in most people) the effect of this angle is multiplied by the length of the tibia 206 to create a significant and problematic deflection at the knee joint 210.
This leg posture is undesirable to a cyclist for several reasons. First, it can be a source of pain in the knee because the forced rotation of the lower leg imparts an axial torque stress on the knee 210, which cannot tolerate a large degree of axial torque. The torque stress is applied to the knee in combination with the repetitive, high-force knee flexion and extension observed when cycling, and thus can cause a rider to experience knee-joint pain that builds up over time. Furthermore, a cyclist typically experiences a loss of pedaling power when employing the leg posture shown in FIG. 2. Because the rider typically pulls up on the pedal 202 (via a toe clip or cleat system as discussed in greater detail below) during the upstroke portion of a pedaling motion, the leg 200 straightens out as the forefoot 104 is no longer forced against the horizontal pedal surface 202. The resulting alternation between medial bending and straightening of the leg 200 (as the leg 200 repeatedly progresses through downstroke and upstroke) causes the knee 210 to trace out a vertically-oriented oval pattern 218 shown in FIG. 2. This back-and-forth lateral motion of the knee while cycling represents a high degree of wasted motion and energy for the cyclist. The result is faster onset of fatigue and erosion of the rider""s capability to apply power to the pedal 202.
FIGS. 3 and 4 depict the use of a wedge 300 to compensate for the natural varus forefoot posture. With the wedge 300 situated between the pedal 202 and forefoot 104, the leg 200 can assume the straight posture shown in FIG. 4 during both downstroke and upstroke, as the ankle joint, lower leg and femur no longer need to compensate for a deviation of the forefoot 104 from its natural varus posture. Thus the knee 210 traces out the desired straight-line pattern 220 as the rider pedals, with a minimum of the wasted motion, power loss, pain and fatigue associated with the poor leg posture depicted in FIG. 2.
FIGS. 5A and 5B depict a well-known pedal system 500 that includes a pedal 502 having a binding mechanism 504 that can receive a cleat 506 attached to the bottom of a cycling shoe 508 worn by the rider on each foot. The cycling shoe 508 has a relatively rigid outsole 510, and the cleat 506 is usually attached to the sole 510 under the ball of the rider""s foot. Typically, each pedal 502 has contact surfaces 512 on either side of the binding mechanism 504 that contact the shoe outsole 510 when the rider pushes down on the pedal 502, to provide a wider shoe-to-pedal contact area and prevent the concentration of pressure under the rider""s foot. This pedal system 500 provides superior cycling performance compared to pedals having toe clips or no foot attachment at all. This is because when xe2x80x9clocked inxe2x80x9d to the pedal 502 with the cleat 506, the rider can push or pull on the pedal 502 in virtually any direction as desired during the pedaling stroke, with minimal loss of power due to poor foot-pedal coupling. Thus with a cleat-and-pedal system the rider can apply a greater amount of power to the pedals over a larger portion of the pedaling stroke.
FIG. 5C shows a variation of the cleat-and-pedal system used with a mountain-bike shoe 550. The mountain-bike shoe 550 is similar in many respects to the standard or road-bike shoe 508 discussed above, with the addition of tread portions 552 on either side of the cleat 506 and elsewhere on the outsole 510. The tread portions 552 facilitate walking with or portaging a bicycle as is often necessary when cycling off-road. To prevent undue wear of or damage to the cleat 506, the tread portions 552 are made sufficiently tall to create a gap or clearance 554 between the cleat 506 and a ground surface 556. The clearance 554 assists in protecting the cleat 506 from damaging contact with a hard ground surface such as rocks, gravel or pavement as the rider walks in the shoes 550.
U.S. Pat. No. 5,860,330 to Code et al. teaches several embodiments of a system for incorporating varus-angular compensation into a cleat-and-pedal system. The first embodiment, depicted schematically in FIGS. 6A-6B, consists of one or more angled shims 600 that are placed between the outsole 510 of the rider""s shoe 508 and the cleat 506. With the shims 600 installed, the cleat 506 is tilted with respect to the shoe outsole 510 so that when the rider mates the tilted cleat 506 with the pedal 502, the tilted cleat 506 is supposed to compensate for the varus angle in a rider""s foot and promote the desired leg posture as shown in FIG. 4.
The shim system suffers from several drawbacks. First, when the cleat 506 is mated with the pedal 502, the angle created between the cleat 506 and the outsole 510 by the shim 600 prevents the outsole 510 from abutting both of the contact surfaces 512 of the pedal 502 (see FIG. 6B). Thus the contact area between the shoe 508 and the pedal 502 is reduced, which concentrates pressure upon the lateral aspect of the rider""s foot when he bears down on the pedal 502. Such a pressure concentration causes foot discomfort and ultimately reduces the efficiency of power transfer to the pedal 502.
Furthermore, as seen in FIG. 7 the shim system taught by Code creates difficulty when used with the mountain-bike shoe 550. With the shim 600 in place, the lower edge of the cleat 506 extends very close to the ground surface 556, or even protrudes beyond the plane defined by the bottom edges of the tread portions 552. This arrangement exposes the cleat 506 to damage and wear from the resulting increased contact with the ground 556 as the rider walks in the mountain-bike shoe 550. Moreover, having been made more prominent by the addition of the shim 600, the cleat 506 concentrates pressure on the ball of the rider""s foot as the rider steps on it while walking. The discomfort thus created can be a significant problem, as it is common for an off-road rider to walk his bicycle several hundred yards or more at a time when he must pass through areas that are either too difficult for bicycle travel or are deemed mandatory walking paths due to trail erosion, excessive pedestrian traffic, etc. Less frequently but significantly nonetheless, a serious rider""s walking distances can extend into many miles when the rider""s bicycle has sustained such excessive damage so as to be unrideable.
The second embodiment taught by Code comprises a cycling shoe with a plate hinged to the underside of the outsole beneath the ball of the rider""s foot. The cleat is attached to the hinged plate, which is adjustable via a screw mechanism to set a varus-compensation angle for the cleat. Whether this adjustable-plate shoe is effective or not in promoting the desired leg posture for the rider, it suffers from several drawbacks that make it an unacceptable solution to the varus-angle problem. The Code shoe is likely to be very heavy, as it must incorporate extra parts such as a rigid plate, a hinge that attaches the plate to the outsole, a screw adjustment mechanism, etc., to an otherwise standard cycling shoe. It is well known that excessively heavy equipment is disfavored in the cycling industry. Moreover, the inclusion of these extra parts and mechanisms also makes the Code shoe likely to be delicate and unreliable, and difficult and expensive to manufacture as compared to a cycling shoe that lacks these additional parts.
Both the Code shoe and the shim system share an additional disadvantage in that both systems increase the distance between the shoe and the pedal axle, which reduces pedaling efficiency by magnifying the effects of those forces encountered in a pedaling downstroke that are not directed downward on the pedal. Thus, energy-robbing bending and torsional effects are undesirably magnified.
Another embodiment taught by Code and otherwise typical of the prior art is a pedal having a built-in varus-compensation angle that is either fixed or adjustable. As a general matter, building a tilt into the pedal as opposed to the shoe is not an economical solution for a cyclist who owns more than one bicycle, e.g. one owning a mountain bike and a road bike, or a xe2x80x9cpracticexe2x80x9d bike and a xe2x80x9cracexe2x80x9d bike. Such a cyclist must then purchase a pedal set for each of his bicycles in order to facilitate the varus-compensation benefits for all of them. Where the desired tilt is built into a shoe, the cyclist need only purchase a single pair of shoes that is usable with all of the bicycles that he owns. With regard to pedals having a built-in varus angle adjustment device, such pedals are undesirable for the same reasons outlined above regarding the adjustable-angle shoe taught by Code. That is, they are likely to be heavy, unreliable, delicate, difficult to use and expensive to manufacture.
Other prior-art approaches to the varus-angle problem have restricted the solution to a relatively small proportion of the cycling population. Typically, there have been custom (and often heavy) equipment modifications that address the most extreme cases of forefoot varus. However, these solutions not only leave out most of the population but also require the knowledge, skill and expense of an orthopedic specialist. This represents a significant hassle and time commitment for the average cyclist who has a varus forefoot and can benefit significantly from corrective equipment. These average cyclists thus miss out on needed treatment because a sound, quick, easy-to-use xe2x80x9cmass-marketxe2x80x9d solution does not exist.
FIG. 7A shows a front cross-section of a foot 700 including metatarsals 702 and interosseus muscles and ligaments 704. It can be seen that the foot 700 has a lateral arch configuration that helps the foot absorb vertical loads in the manner of a leaf spring. That is, when under load the lateral arch of the foot 700 compresses as shown in FIG. 7B. When the arch compresses in this manner, the interosseus muscles and ligaments 704 are stretched and forced to bear part of the load; repeated and/or prolonged stretching or loading of these structures can cause a condition known as xe2x80x9chot foot pain.xe2x80x9d This condition is common when cycling, as the lateral arch is repeatedly compressed under relatively heavy loads as the rider presses down on the pedals. Prior known cycling shoes did not incorporate any features tending to address the xe2x80x9chot foot painxe2x80x9d problem.
Thus, a cycling shoe that overcomes the limitations of the prior art is needed.
In accordance with one preferred embodiment a cycling shoe comprises a rigid outsole having a heel portion, a forefoot portion forward of the heel portion, a toe portion forward of the forefoot portion, an upper surface and a lower surface. The lower surface has a pedal contact area underlying the forefoot portion. The pedal contact area defines a base plane, and the upper surface of the outsole is sloped laterally with respect to the base plane along substantially the entire width of the forefoot portion, at a predetermined varus-compensation angle.
In accordance with another preferred embodiment a cycling shoe comprises an upper portion for attachment of the cycling shoe to the foot of a rider, a sole portion lasted to the underside of the upper portion, and a pedal contact area built into the sole portion. The sole portion has a lateral cross-section in the area that underlies the ball of the rider""s foot and the lateral cross-section incorporates a wedge shape that tilts the rider""s foot with respect to the horizontal at an invariable varus-compensation angle.
In accordance with still another preferred embodiment a method of improving a cyclist""s leg posture while pedaling comprises interposing a sole of a cycling shoe between the cyclist""s foot and a pedal of a bicycle. The sole has an upper surface that is laterally tilted with respect to the horizontal so that the cyclist""s foot is correspondingly tilted when pedaling. The upper surface is tilted at an invariable varus-compensation angle.
For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention have been described herein above. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.
All of these embodiments are intended to be within the scope of the invention herein disclosed. These and other embodiments of the present invention will become readily apparent to those skilled in the art from the following detailed description of the preferred embodiments having reference to the attached figures, the invention not being limited to any particular preferred embodiment(s) disclosed.